Dynamo-electric machinery.



A. H. MIDGLEY & C. A. VANDERVBLL.

DYNAMO ELECTRIC MACHINERY.

APPLICATION FILED JULY 11,1910.

1,057,759, Patented Apr.1,1913.

Biglf I la.

UMTED STATES .PATENT oFFicE.

ALBERT HENRY MIDGLEY AND CHARLES ANTHONY VANDERVELL, F .ACTON VALE,

` ENGLAND.

DYNAMIC-ELECTRIC MACHINERY.

summation of Letters Patent.

Patented Apr. 1, 1913.

pplieation led July 11, 1910. Serial No. 571,351.

To all 'whomt may concern:

Be it known that we,v HENRY MIDGLEY and CHARLES ANTHONY VANDER- vELL,subjects-of the Kin of Great Britain and Ireland, residin at arple Way,Acton Vale, Middlesex, ngland, have invented new and useful Improvementsin Dynamo- Electric Machinery, of which the following is aspecification. i

This invention relates to dynamo electric machinery particularly of thatclass, in the case of a generator in which the rate of revolution isvariable and is especially applicable to dynamos used for train lightingin conjunction with a battery of accumulators.

This invention has for its object the construction and arrangement of amachine which if desired can .be used in either direction of rotation,so that in the case of agenerator it will give a constant output atvarying speeds, or a useful current at a constant voltageirrespective ofthe rate of rotation, while in the case of a motor supplied with currentof a variable voltage, a constantspeed is obtained.

This invention consists of a dynamo electric machine in which thebrushes for collecting the useful current are arranged in such apositionthat the coil or coils of the armature short-circuited by thesaid brushes are in an active zone where they are cutting an init-ialmagnetic flux due to wound poles,'

and the current thus' generated in the short circuited coils, asdistinguished from the working current which flows through the larmaturefrom brush to brush,` acts to distort the said initial magnetic flux ina manner hereinafter explained in order to accomplish self-regulation.

If a dynamo electric machine has one magnetic field system act-ing uponan armature and the armature coils short-circuited by the brushes arecentrally situated in the same plane as the magnet-ic iuX,-and if thereaction of the armature Winding is in the same plane as the magneticflux but directly opposing it, it is evident no current would begenerated in the armature winding if the armature were rotated, as lanequal number of conductors on opposite sides of the armature .would becut by a magnetic flux of the same polarity. This position of thebrushes ever, the'magnetic flux be distorted by some means to one sideof the center of the plane ofthe short-circuited coils, then current isgenerated in the armature conductors when rotatedin' one direction, and,if the field be distorted in a similar way to the opposite side and thearmature is rotated lin the reverse direction, then the currentgenerated in the armature conductors would still be in the samedirection.

It is well known that in every armature in addition to its workingcurrent there would be another and local current produced in the coilsshort-circuited by the brushes if such short-circuiting took place at amoment when the coil is not situated in a neutral zone, and themagnitude of such local current depends, ceterz's pam'bus, upon thestrength of the magnet-ic flux and the speed at which the armaturerotates. In .carrying out our invention, we utilize this property ofithelocal current in the short-circuited coils to produce across-magnetizing force in the armature to dist-ort the magnetic iuX toone side of the center of the plane of the short-circuited coils, and wealso utilize the reaction of the working current in the armature windingto weaken the magnetic flux as the speed of the armature increases inorder to ,pbtain the desired self regulation.

In order that the invention may be the better understood,` we Will nowproceed to describe the same in relation to the accompanying drawing,reference being had to the let-ters and figures marked thereon.

ALike letters refer to like parts in the various figures.

lFigure 1 is a diagrammatic represent-ation of our invention as appliedto a variable speed dynamo. Fig. 2 illustrates diagrammatically thechord winding of the armature which is preferably used, and indicatingin heavy lines the short-circuited coils. Fig. 3 is a diagrammaticrepresentation of the magnetic system showing the distortion of theinitial magnetic flux from what may be termed subsidiary poles throughmain poles for a clockwise rotation of the armature, the undistortedflux and distorted uX being represented by thin and thick dotted` linesrepresentation of an armature having diametrical drum Winding, the shortcircuited coils being indicated in heavy lines.

In order to show one way in which the invention can be carried intoeffect we wind the armature a on the chord. principle preferably in themanner such as is described in British Patent No. 21988 of 1908 and isillustratedinFig. 2 of the accompanying drawings, and to the commutatorof the armature a we provide one set only of brushes c. Each brush c isadapted to shortcircui't one or more individual armature coils 0l (shownin thicklines) such shortcircuiting taking place while said coils arecutting the magnetic flux from the subsidiary poles. We provide fieldmagnets c with such subsidiary poles f disposed midway between the mainpoles g, these subsidiary poles being provided with a winding h inconjunction with means such as a shunt circuit for energizing the saidwinding from the brushes c c of the generator. The main poles gthemselves are not provided with any winding at all, but as thesubsidiary poles f are excited independent of the main poles, themagnetic flux excited by the windings of the subsidiary poles f willalways have one direction so far as the subsidiary poles are concernedand will never be reversed. The brushes c c are so placed that the'short-circuited coils d cut the magnetic flux due to the subsidiarypoles f and the local current generated thereby in the saidshort-circuited coils d will be reversed if the direction of rotation isreversed. The local current generated in the short-circuited coils dsets up a cross-magnetizing force which distortsthe magnetic' ux fromthe path z' into the path k approximately at right angles to thesubsidiary poles f, which distorted flux thus generates the workingcurrent in the armature winding a. It will be noted that as thisdistortion of the magnetic iux is produced by the local current of theshort-oircuited coils d such distortion will be directed toward one sideor the other according to the direction of rotation of the armature, andthe working current taken from .the vbrushes c c will always be )in onedirection. It will be understood that as the working current taken fromthe armature a increases, the armature lreaction produced thereby beingin approximately the saine lplane andof opposite polarity to themagnetic fiuX'due to the subsidiary poles f, the

said flux is weakened and consequently the local current generated inthe short-circuited coils d is reduced while the output is keptpractically constant.

` It must be understood that although we have described the armaturewound with a chord winding as one way of carrying out the invention wemay use an ordinary diainetrical drum Windinggas shown in Fig. 4, but weprefer the chord winding, part1cularly the specific form of chordwinding referred to.

We are aware that it has been proposed to construct a self regulatingdynamo having two magnetic fields which do not coalesce and which havedifferent paths, the axes of these fields being displaced relatively toeach other approximately 9()o and acting upon a single armature with oneor two windings, .one field never becoming reversed so that a ond iieldchanging with the direction of r0- tation is A brushes app'ertainingthereto, and the second field changing with the direction of r0- tationand induced by the above mentioned current so that the armature brushesappertaining thereto have a constant polarity independent of thedirection of rotation; a necessary featurebeing that the direct actionof each field on the winding which does not appertain to it shall besmall. In our invention only a singlev magnetic flux results which actson all thearmature conductors collect the working current and set uplthe self-regulating features.

It is quite common to use the reactions in an armature or in thewindings of an armature, or in so much of a winding as is for the'moment in circuit between brush and brush to give a' regulating eect,but the function is quite different from that of currents generated in acoil or coils when bridged at the commutator by a brush in accordancewith our invention. In all ordiwhich the working current is taken are,for the purpose. of sparkless commutation, either set at such ositionsthat the indiy vidually short-circulted coils are in a neutral field,where therefore no local short-circuit' current would be generated, orelse they are setat such a position, by being given a lead or, by being.set near a commutating pole, that any electromotive force induced inthe coils tends to reverse or neutralize any short* circuited current inthem, whereas in our invention the brushes are s o placed that the`'coil or coils locally short-circuited thereby are in the active zone ofthe magnetic flux.

tion, we claim as new and desire to secure by Letters Patent In a dynamoelectric machine, in combination, a generator armature, brushessuiiciently broad to short circuit individual `with windings to excitecurrent in said short circuited armature coils n rotation of thearmature, unwound poles arranged approXimately at right angles to theplane of the said short circuited armature coils to permit the diversionofthe flux through the and only one set of brushes is requisite to.

coils in the said armature, poles provided supplied from the armature,4

nary dynamos and motors the brushes from Having thus fully described ourinvensaid poles due to the iniuenee of the seid names to thisspecification in the presence short circuited coils so that suehdiverted of two subscribing Witnesses. flux is utilized to produce theWorking cur- ALBERT HENRY MIDGLEY. rent in the external circuitconnected to the CHARLES ANTHONY VANDERVELL. said short eireuitingbrushes, substantially Nitnessesr as described. RICHARD A.HOFFMANN,

In testimony whereof We have signed our CHARLES J. R. BULLOUGH.

Copies of this patent may be obtained for ve cents each, by addressingthe Commissioner of :Patente-T Washington, D. G.

